Question about 2002 Chevrolet Tahoe

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No heat when moving. when i sit still i get a lot of heat. I replaced the thermostat, coolant level is ok. both heater core hoses get hot.all doors and heat settings work. temp gauge stays right at 200 while driving or sitting. but soon as i drive 2 blocks it goes from really hot to cool air.

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  • kevin
    kevin Oct 22, 2013

    if the coolant was not circulating or impellors corroded would i not overheat? what do you think the chances are I got bought a bad thermostat?



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If you have a vapour lock your engine will create steam easily but the coolant doesn't circulate. Or it is possible that your impellors on your water pump have corroded

Posted on Oct 22, 2013


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Posted on Jan 02, 2017

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SOURCE: heater does not blow hot air on full heat setting

the problem is caused by the motor that operates the air temp blend door motor in the heating ducts, it blends air between AC and heater core tro give desired outlet temp.

Posted on Dec 12, 2008

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SOURCE: cooling temp sensor

Should be located on the lower intake on right or left toward the front. Two wires watch cause there's and air temp that might look the same.

Posted on Mar 26, 2009

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SOURCE: I have a 1997 Chevy Malibu that is over-heating.

if you do not turn the a/c on, do the fans cycle? turning on the a/c will signal fan demand - this indicates the the fan and circuits are OK. if the fan cycles with the a/c off, we can move away from a fan issue. if not, look into that. have you tested the rad cap? i believe this model has one cap on the expansion tank and no rad cap, if i remember correctly. i have actually run into one of these cars where an incorrect cap was installed, causing similar symptoms. it sounds as if you know what you are doing, but is there any possibility that there is an air lock in the cooling system? if there is heat coming out of the vents when the car is hot, there is probably no issue there, and also likely means the waterpump is ok. let me know and we'll talk later if necessary, good luck!

Posted on Apr 02, 2010

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SOURCE: temperature stays consistant while driving but

That does not seem too abnormal to me. I believe you have a 195 degree F thermostat, so you should probably be a bit cooler than 230 that is for sure. You have got an engine temperature sensor, should be located on cooling port on intake, you have a coolant temperature sensor on rad. Have you put in a new thermostat?

Posted on Oct 02, 2010

  • 2 Answers

SOURCE: 04 Chev. Avalanche 1500 Z71 5.3 125K mi. Temp

Normally the engine operates at 195F, if you did not replaced thermostat with another one at 185F. If the temperature has a tendency to rise up, the reason is a partially obstructed cooling system or/and a bad thermostat.
The first part of the cooling system that gives up is the heater core, because the coolant flowing channels are thin. You got a good advice but not the best one. It is the time for a coolant flush in your car. To do do it right then you need time. Plan ahead for a week end. With a cooled engine, start as your friend advised you with the heater core hoses. Disconnect both of them, but the dirt has to go out of your car, so with a garden hose back flush it and let the dirt to get out of your cooling system. After you will get clean discharge, it is the time for coolant bottle, remove it, discharge the used coolant and clean it. The third to come is the radiator. Open the drain cook, or disconnect the lower radiator hose, and disposal used coolant properly. Now open the radiator cap and flush with water the radiator till discharge will be clear. You think that you are done? Not yet. There is half of old dirty coolant trapped in the system.
Install everything, and connect all coolant system hoses, radiator, heater core and coolant bottle. Now you have to run your car with water. Fill out the cooling system with distilled water, start engine, turn on the heater high, and run till upper radiator hose get hot. That means the thermostat opens.
Let the engine to cool down, open the radiator cap, and draining cook or lover radiator hose and drain everything. You can use flush detergent if you wanted at this stage, but flushing with detergent will add 4 more hours, because detergent is colorless and you have to guess how many fill and drain processes do do to get rid of it. I do not do it, but if your cooling system is very dirty you have to do it. After the last drain, fill the cooling system with concentrated antifreeze and 30% distilled water. The reason is because it is more water trapped inside the cooling system. The goal is to reach 50/50 concentration. You need a coolant tester to find this. Start the engine and add coolant til radiator is full. Install the radiator cap and bleed the system. After driving you car for a day or so, let engine to cool down, open the radiator cap check the concentration of coolant with the tester and add antifreeze or distilled water as necessary. It is a good idea to replace the thermostat while flushing the radiator. This procedure has to be done every 2 to 3 years. It is up to you to decide to use RED GM Dex-Cool or GREEN Prestone antifreeze.
In all my cars I have replaced Dex-Cool with Prestone, but I flush the system every 2 years, and I never had a cooling system problem in all my cars.

Posted on Nov 14, 2010

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No heat air blows just cold air

Let car cool down then check coolant level. If it is low it won't allow coolant to pass through the heater core. If it is ok it could be stuck thermostat or bad heater core. If lines coming out of heater core are hot on both hoses it is good, if only one is hot then it is a plugged heater core. You can take hoses off and use a water hose to flush out heater core from one hose then back the other way through the other hose. Hope this helps!

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Could be a stuck thermostat... or low coolant level. feel hoses going to heater core, if only one is hot while car is warmed up. i would say the heater core is plugged because this is where you get the heat for inside of car ! hot coolant goes through heater core and a fan blows it out to heat inside of car. if both are hot then the heater core is ok.

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Hello Pall.

There are a few things that will cause a no heat problem.

First of all, check the coolant level. If it is very low, the coolant will not flow through the heater core.

Next is the thermostat. If it sticks open the coolant will flow through the radiator all the time taking away all the heat developed in the engine.

If those check out OK, then check the two hoses that carry the coolant to the heater core.
Both should be hot to the touch and very close to the same temperature.
If one is cooler than the other there is a restriction in the heater core and it will need to be flushed out or replaced.

Next is to make sure the temperature control on the heater box is working.
This is controlled by the dial on the dash and activates a motor which moves a door in the heater box that controls hot/cold airflow. Sometimes the motors on these pickups would go open circuit and quit working.

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Check the level of the antifreeze (coolant) in your reservoir. If it is just a little low, it will not flow properly through the heater core.

If the coolant level is ok, check the temperature of the hoses going in and out of the heater core. Your Taurus is not equipped with a heater control valve, so there should be hot coolant circulating through the heater core at all times. If one hose is really hot and the other feels cool or cold, then your heater core is most likely clogged with corrosion and debris. (If this is the case, I recommend a complete cooling system flush)

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Follow these steps:

Check coolant level, then start engine until it is warm and the thermostat opens. You will tell when it does when the needle on your temp gauge goes cold when it reaches around 180-200* and then goes back up. Now turn on your heater full blast and go to the engine compartment. You will see a heater valve located on the passenger side, next to the washer reservoir. It is a black thing with 4 heater hoses connected to it. Feel the hoses. When everything is working correctly it should be like this:

Hose going to waterpump will be hot
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1. If only 1 heater core hose is hot, heater core is clogged--
UNCLOG: remove 2 hoses going to heater core when engine is cool, hook water hose end to one of the sides and flush out gunk from heater core. Reconnect hose and you should be good.

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